A vehicle seat has a foam trim pad which contorts the occupant's torso to provide support at varying levels of comfort depending on the frame, suspension and adjustment system which supports the trim pad. Since one size does not fit all occupants, a vehicle seat can be provided with an adjustment device to provide arbitrary articulation to the frame assembly with the goal of altering the supportive contours and thereby improve perceived comfort.
U.S. Pat. No. 5,137,329, entitled: "Articulated Lumbar Support for A Seat" provides a user adjustable lumbar support apparatus for inclusion in a seat back, comprising an essentially rigid back plate, a front plate having an orthotic lumbar support contour and a multi-chambered fluid actuator including at least a pair of independently inflatable chambers arranged vertically one chamber above the other. The fluid actuator is a bladder containing separated chambers. Fluid under pressure is admitted and vented separately to and from each chamber to alter the positional relationship of the front plate to the back plate so the lumbar support contour can be adjusted to a position giving optimum support at a desired elevation along the seat back. The three elements are joined by an elastic strap.
The fluid actuator merely raises or lowers to the pressure point of the front plate to a desired elevation. The fluid actuator allows some rotational movement of the front plate relative to the back plate. However since the front plate is coupled to the rear plate by an elastic strap, only a limited amount of vertical movement is permissible and thus providing a limited amount of adjustability of the seat for the occupant.